Current identification of nerves during surgery utilizes non-quantifiable criteria such as anatomy, texture, color, relationship to surrounding structures to distinguish nerves from non-nerve tissues. In instances of trauma, tumor invasion or infection, nerve identification using the above criteria may be challenging. We have identified a peptide sequence, Nerve Peptide 41 (NP41) through phage display that preferentially binds to peripheral nerves compared to adjacent non-nerve tissue after systemic administration. Systemic injection of this peptide into rodents results in specific nerve labeling beginning at 2 hours. Useful nerve-specific fluorescence lasts up to 8 hours following a single intravenous injection, allowing more accurate identification of small and buried nerve branches when compared to visualization with white light reflectance alone. In this study, we propose to accomplish the following specific aims: 1) Show proof of concept in using NP41 for surgical molecular guidance in animal models and in excised human nerves of the head and neck, 2) Show proof of concept in using nerve peptides for to label the autonomic nerves coursing along the prostate gland in animal models and in excised human specimens, 3) Optimize NP41 in preparation for preclinical testing A nerve specific fluorescent label has the potential to provide surgeons with a molecular marker visualizable in real time to distinguish nerve from non-nerve tissue, thereby improving surgical accuracy and avoid inadvertent injury. Together, the above studies will yield several proof of concept studies in animal models of head and neck surgery and prostate surgery to test the surgical outcome using fluorescence labeling of nerves with the aim toward eventual use of NP41 during head and neck surgery and nerve-sparing radical prostatectomy in patients.